1. Field of the Invention
The present invention relates to telecommunications. In particular, the present invention relates to format for a medium sensing measurement histogram report.
2. Description of the Related Art
The IEEE 802.11k standard relates to radio resource measurements. In particular, IEEE 802.11k Draft 1.0 specifies a “Medium Sensing Time” histogram measurement report that is used for measuring the distribution of busy and idle times on the medium. The measurements are marginal distributions, and as such, do not provide information that would be useful to a station management entity for determining whether a given audio/video stream would be admissible on the medium, based on the Quality of Service (QoS) requirements for the audio/visual stream for throughput, latency, jitter, and medium servicing requirements.
Accordingly, the measurement, as proposed, is not particularly useful for determining whether a Traffic Specification (TSPEC) can be admitted for a QoS flow. QoS flows generally have requirements for service times (a stream must get a poll approximately every Tservice seconds, in which the medium would be construed as “busy,” and would, in general, allow for idle times of Tidle seconds. By obtaining an estimate of busy and idle times, and communicating the estimates to higher layers, a convergence layer, an application layer, or a station management entity would have information relating to whether the medium may support the admission of a particular AV or Voice Over IP (VoIP) stream.
FIG. 1 shows the field format 100 of a conventional Medium Sensing Time Histogram Report, as set forth in the IEEE 802.11k Draft 1.0. The Channel Number field is used for indicating the channel number to which the Medium Sensing Time Histogram Report applies. The Channel Band field is used for indicating the frequency band for which the measurement report applies. The Actual Measurement Start Time field is set equal to the value of the Time Synchronization Function (TSF) timer of the measuring Station (STA) at the time at which the measurement is started. The Measurement Duration field is set equal to the duration over which the Media Sensing Time Histogram Report was measured and is expressed in Time Units (TUs).
The Medium Sensing Measurement Subtype field is used for indicating the subtype of Medium Sensing Time Histogram Report. The Request Polling Interval (RPI) Threshold field is used for identifying a received power level threshold as seen at the antenna connector. The RPI Threshold field is used for determining when a Medium Sensing Interval begins and ends, while collecting information for the RPI Time Histogram.
The Bin Offset field is used for indicating the position of the first bin and is expressed in microseconds. The Bin Duration field is used for indicating the time interval during which Medium Sensing Events are counted to be in a bin and are expressed in slot times. The Number of Bins field is used for indicating the total number of time intervals that are covered by the time histogram. The Total Number of Medium Sensing Intervals is used for indicating how many intervals have been counted during the measurement. Lastly, the Medium Sensing Time Histogram Report contains fields for indicating the measured densities of each of the N time intervals in the specified channel over the measurement duration.
Table 1 indicates the definitions for the Medium Sensing Interval, as set forth in the IEEE 802.11k Draft 1.0.
TABLE 1Medium SensingMedium SensingMedium SensingMeasurement TypeMeasurement NameInterval0RPI Time HistogramTime interval duringwhich RPI is above thespecified RPIThreshold1Clear Channel AssessmentCCA Idle Time(CCA) Idle TimeHistograminterval2CCA Busy TimeCCA Busy TimeHistograminterval3Network Allocation VectorInitial NAV time value(NAV) Busy Timewhen setHistogram4-255ReservedReserved
To compute the Bin i density, Bi, 0=i<N, the STA initializes all Bin values to zero. During the measurement duration the STA monitors the measurement channel for the medium sensing intervals of the requested subtype. The length (duration) of the detected interval determines which bin count is to be incremented. If the detected interval has a duration time t with:i0+(i*Δi)≦t<i0+((i+1)*Δi) for i<N−1, and  (1)i0+(i*Δi)≦t for i=N−1,  (2)withi0=bin offset,  (3)Δi=bin interval,  (4)i=bin index, and  (5)N=number of bins,  (6)then the interval count in Bin i is increased by one, except when the bin contains a count of 255. During the Medium Sensing Measurement, a histogram is generated that represents the probability distribution of Medium Sensing Time Intervals.
If a measurement request is received in which i0+((N−1)*Δi) is greater than the requested measurement duration, the measurement request is deemed invalid and is ignored.
What is needed is a way for admission control units that admit TSPECs to have a measurement of joint densities of idle and busy times.